The present invention generally relates to orthopedic surgery and, more particularly but not exclusively, to surgical assemblies and methods for correcting hallux abducto valgus.
Hallux abducto valgus (HAV) is a deformity primarily of the forefoot involving lateral deviation of the great toe, and medial deviation of the first metatarsal.
In an HAV deformity, a point is reached in which the muscles migrate laterally beyond the 1st metatarsal phalangeal joint lateral boundary. Once this stage has been reached, the deformity is self-feeding, as the muscles gain inordinate mechanical advantage, causing further angular deviation so that the hallux abducto valgus deformity becomes progressively more pronounced.
The severity of HAV deformities has traditionally been quantified through measurements of X-ray radiographs. The first of the two most common measurement or quantification techniques for hallux abducto valgus deformity is the 1st intermetatarsal (IM) angle. The 1st IM angle is the angle defined by the intersection of lines made along the longitudinal axes of the first and second metatarsal shafts. This angle is normally about six degrees; the upper normal limit is about nine degrees.
The second measurement that defines an HAV deformity is the 1st Metatarsal Phalangeal Joint (MPJ) angle, which is defined by the intersection of lines made along the longitudinal axes of the first metatarsal shaft and the proximal phalanx of the hallux, alternatively referred to as the first toe, or great, toe.
A normal maximum for a 1st MPJ angle is between nine and ten degrees. An MPJ angle measurement of 12 degrees would be almost uniformly regarded as abnormal.
An HAV deformity typically includes both an abnormally high 1st IM and an abnormally high 1st MPJ angle; with a severe HAV deformity including a 1st IM angle of 15 degrees or more; and a 1st MPJ angle of 35 degrees or more.
A severe HAV deformity, in addition to being unsightly, is painful in most footwear, even footwear having extra wide widths. Sufferers of severe HAV deformities generally are limited to wearing non-aesthetic shoes that have a special out-pocketing in the forefoot to accommodate the displaced bones.
In some instances of HAV, for example in moderate HAV bone deviation, surgical correction is an aesthetic consideration. In other instances of HAV, surgical correction, particularly in severe HAV bone deviation, is a medical imperative, for example to prevent ulceration, infection, and/or amputation.
Surgical correction of HAV deformity often requires osseous correction, for example an osteotomy comprising a bone wedge of the proximal and/or distal first metatarsal; and an osteotomy comprising a bone wedge of the first proximal phalanx. In addition, surgical correction usually requires remodeling of a bunion deformity, comprising, inter alia, a medial out pocketing of bone over the 1st MPJ.
Osseous correction may not produce satisfactory long-term results due to continued abnormal forces exerted by the muscles and ligaments, which often cannot be fully realigned during surgery; and/or continued biomechanical imbalance in the foot during gait.
The abnormal forces pull the bones of the 1st MPJ and 1st metatarsal toward the original abnormal angles. Malunion and non-union have also been recorded in cases of HAV osseous correction.
Relevant Prior Art includes U.S. Pat. No. 4,159,716 (Borchers).